Valve-unloading mechanism for reciprocating pumps



g- 5, 9 v J. E. MILLER 3,459,363

VALVE' UNLOADING MECHANISM FOR RECIPROCATING PUMPS Filed Dec. 21, 1967 2 Sheets-Sheet 1 INVENTOR JOHN E. MILLER A BY ATTORNEY Aug. 5, 1969 J. E. MILLER 3,459,353

VALVE'UNLOADING MECHANISM FOR RECIPROCATING PUMPS Filed Dec. 21, 1967 2 Sheets-Sheet 2 v INVENTOR 3 j a g ua/m/ E. MILLER *8 2 v q BY ,//22%/ gLm ATTORNEY United States Patent Office 3,459,363 VALVE-UNLOADING MECHANISM FOR RECIPROCATING PUMPS John E. Miller, Dallas, Tex., assignor to United States Steel Corporation, a corporation of Delaware Filed Dec. 21, 1967, Ser. No. 692,557 Int. Cl. F0411 49/02, 49/06, 39/00 US. Cl. 230-24 5 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an improved mechanism for unloading the suction valve of a reciprocating pump.

A pump of the type to which the invention is applicable includes one or more cylinders (commonly three) and respective plungers mounted for reciprocable movement in the cylinders. The plungers are driven through individual crossheads and connecting rods and usually a common crankshaft. Each cylinder has a suction valve and a discharge valve, or two of each if the pump is doubleacting. Reference can be made to Redman Patent No. 2,519,501 for an exemplary showing of such a pump, altough it is apparent my invention is not limited to use with a pump of this specific construction.

On occasion it may be necessary to stop discharge of fluid from the pump while keeping the pump in operation and maintaining flow through the cylinders. The simplest way of accomplishing this is with a valve-controlled bypass connected between the discharge and suction sides of the pump. A by-pass has disadvantages that considerable time is taken to change the valve settings (about 15 seconds minimum), and there is a loss of discharge pressure. To overcome these difiiculties, it is known to equip the pump with an unloading mechanism which holds the suction valve open as long as flow is to be stopped. Thus fluid merely flows in and out the cylinder through the suction valve. The discharge valve remains closed, and there is no loss of pressure therebeyond. As explained hereinafter, an unloading mechanism must act quickly and at the proper time in the pumping cycle. Previous unloading mechanisms with which I am familiar have been unduly complicated to achieve the necessary speed and synchronization.

An object of my invention is to provide an improved and simplified unloading mechanism which operates quickly and in proper synchronism with the pump.

A more specific object is to provide an improved unloading mechanism which is actuated electrically through a proximity switch on the pump drive and includes a solenoid-operated rod for holding the suction valve open.

In the drawing:

FIGURE 1 is a longitudinal sectional view of a portion of a pump equipped with my unloading mechanism; and

FIGURE 2 is a schematic wiring diagram of the preferred electric circuit embodied in the mechanism.

FIGURE 1 shows a portion of a pump which includes a cylinder 10, a plunger 12 mounted for reciprocable movement in the cylinder, and a stutfing box 13 surrounding the plunger where it enters the cylinder. The plunger is connected to a suitable drive, the crosshead of which is shown diagrammatically at 14 in FIGURE 2. The cylinder carries a suction valve pot 15, a discharge atented Aug. 5, 1969 valve pot 16, and a cylinder head 17. The valve pots have chambers which communicate with the usual suction and discharge manifolds. The suction valve includes a seat 18 fixed within the pot 15 and a cooperating disk 19. A spring 20 bears against disk 19 and against a bumper 21 integral with the cylinder head 17 and thus urges the disk to its seated or closed position. The discharge valve can be constructed similarly; hence I have not enumerated the individual parts. Since pumps of this construction or equivalent are well known, no more detailed description is deemed necessary.

The suction valve pot 15 carries an unloading mechanism 25 constructed in accordance with my invention. The mechanism comprises a bracket 26 fixed to the bottom of the valve pot, and solenoid 27 fixed to the bracket, and a vertically movable lifter rod 28 attached to the armature of the solenoid. I fit a bushing 29 in the bottom of the valve pot. Rod 28 extends through the bushing to the proximity of the valve disk 19. The rod is slidable within the bushing, with O-rings 30 providing a seal. When solenoid 27 is energized, the rod moves upwardly into engagement with the valve disk and holds the valve open against the action of spring 20. Otherwise the rod clears the disk and allows it to open and close normally.

During a suction stroke of the pump plunger 12 travels toward the left, as viewed in FIGURE 1. The suction valve is open and the discharge valve closed. During a discharge stroke, the plunger travels toward the right and the position of the valves normally is reversed. The crankshaft of the pump turns a half revolution during each stroke. Operation of the unloading mechanism must be synchronized with plunger movement so that rod 28 engages or releases the valve disk while the plunger is making a suction stroke. The rod must move with sufiicient speed that it completes its motion before the plunger completes its suction stroke. Otherwise the full discharge pressure of the pump would be on the disk at the time the rod is operating. My unloading mechanism includes a circuit for automatically synchronizing its operation in this manner. FIGURE 2 shows my preferred circuit schematically. In a multiple-cylinder pump I provide separate circuits for each cylinder, since the plungers make their suction strokes at different times. For double-acting pumps, I provide separate circuits for the suction valves at each end of the cylinder.

My preferred circuit includes a master switch 32, a normally open proximity switch 33, and a solid-state amplifier 34. The proximity switch and amplifier per so are known devices available commercially, for example, the Micro Switch proximity switch and the 40 FL 1 amplifier supplied by Honeywell, Inc. For descriptions, reference can be made to a printed publication by the supplier entitled Data Sheet 213 b, Supplement to Catalog 85. I connect the power input terminals of the amplifier to lines 36 and 37 which are connected to a suitable power source. I connect the proximity switch to the control terminals of the amplifier. The master switch 32 has a load position, which it normally occupies, and an unload position. I mount the proximity switch 33 adjacent the crosshead 14 (or some other reciprocating part) at the position the part occupies at the conclusion of a discharge stroke. The proximity switch closes momentarily at the end of each discharge stroke, but as long as the master switch 32 is in its load position, the circuit is not actuated, and the suction valve opens and closes in its usual sequence.

The circuit components include three relays A, B and C. I connect the coil of relay A in series with the unload contact of the master switch 32 across lines 36 and 37. Relay A has three normally open contacts A A and A I connect the coil of relay B in series with contact A across the output terminals of amplifier 34 .When I move the master switch 32 to its unload position, relay A is energized and sets up relay B through contact A The next time the proximity switch 33 closes, relay B is energized momentarily. Relay B has a double-throw, doublepole contact B I connect the normally open poles of the contact B contact A and the coil of relay C in series across lines 36 and 37, whereby relay C is energized with relay B. Relay C has three normally open contacts C C and C When relay C is energized, it locks in through contacts C and A and thus remains energized even though relay B is energized only momentarily. I connect contact C in series with solenoid 27, whereby the solenoid is energized with relay C.

When I return the master switch 32 to its load position, relay A is deenergized. Usually the proximity switch 33 is open at this time and relay B deenergized. I connect the normally closed poles of contact B in series with contact C and the coil of delay C, bypassing contact A whereby relay C remains energized even though both relays A and B now are deenergized. I connect contact C in parallel with contact A whereby relay B remains set up even though relay A is deenergized. The next time the proximity switch 33 closes to energize relay B, the normally closed poles of contact B open and break the current path through the coil of relay C. Thus the circuit returns to its normal deenergized state, the lifter rod 28 releases the valve disk 19, and the pump resumes its normal operation.

From the foregoing description, it is seen that my invention affords a simple effective mechanism for unloading the suction valve of a reciprocating pump. The circuit can be actuated only at the conclusion of a discharge stroke. Thus the lifter rod can engage or disengage the valve disk only while the ensuing suction stroke is taking place. The lifter rod does not force the suction valve open against the discharge pressure of the pump nor allow it to slam closed under this pressure. The action of the relays and solenoid is sufliciently rapid that the lifter rod moves fully into position before completion of a suction stroke. Although I require separate circuits for each cylinder, only a single master switch suffices.

While I have shown and described only a single embodiment of my invention, it is apparent that modifications may arise. Therefore, I do not wish to be limited to the disclosure set forth but only by the scope of the appended claims.

I claim:

1. In a reciprocating pump which includes a cylinder, a plunger mounted in said cylinder for reciprocable movement, drive means operatively connected with said plunger, and suction and discharge valves on said cylinder, said plunger having a suction stroke during which said suction valve is open and said discharge valve closed,

and a discharge stroke during which the position of said valves normally is reversed, the combination therewith of an improved unloading mechanism comprising a solenoid, means mounting said solenoid on said suction valve, a lifter rod operated by said solenoid, and an electric circuit connected to said solenoid for selectively energizing and deenergizing it to move said rod to a position in which it holds said suction valve open and a position in which it allows said suction valve to operate normally, said circuit including control means for permitting said solenoid to be changed between its energized and deenergized states only when said plunger is making a suction stroke.

2. A combination as defined in claim 1 in which said last-named means includes a switch operated by said drive means at the end of a discharge stroke of said plunger.

3. A combination as defined in claim 2 in which said switch is a proximity switch mounted adjacent a reciprocating part of said drive means at the position the part occupies at the conclusion of a discharge stroke.

4. A combination as defined in claim 1 in which said suction valve includes a. valve pot integral with said cylinder, a seat mounted in said pot, a disk engageable with said seat, and a spring urging said disk into engagement with said seat, said mounting means including a bracket fixed to the outside of said pot on which said solenoid is mounted, said rod extending into said pot and being engageable with said disk to hold the disk out of engagement with said seat against the action of said spring.

5. A combination as defined in claim 1 in which said circuit includes a master switch having a load position in which said suction valve operates normally and an unload position in which said rod holds said suction valve open.

References Cited UNITED STATES PATENTS 337,803 3/1886 Worth 230222 1,956,765 5/1934 Jones 230- 2,274,338 2/ 1942 Cody 230-24 2,681,177 6/1954 Hartwell 23024 2,730,296 1/1956 Hartwell 230-24 2,785,638 3/1957 Moller 103227 X 3,259,077 7/1966 Wiley et al. 103227 3,273,512 9/1966 Yoshida et al. 103-227 X 3,273,786 9/ 1966 Newton 230-23 3,327,640 6/1967 Townsend 103227 X DONLEY I. STOCKDIG, Primary Examiner W. J. KRAUSS, Assistant Examiner US. Cl. X.R. 

